ConstraintLayout初探

ConstraintLayout性能解析

常用属性

类似于RelativeLayout的属性

layout_constraintStart_toStartOf

app:layout_constraintStart_toStartOf=”@id/text1”

该控件与text1左对齐

app:layout_constraintStart_toStartOf=”parent”

该控件约束在布局最左端

layout_constraintStart_toEndOf

app:layout_constraintStart_toEndOf=”@id/text1”

该控件在text1的右端

其它以此类推

<TextView
    android:id="@+id/text1"
    android:layout_width="100dp"
    android:layout_height="80dp"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintBottom_toBottomOf="parent"
    android:background="@color/red"/>
<TextView
    android:id="@+id/text2"
    android:layout_width="0dp"
    android:layout_height="50dp"
    app:layout_constraintStart_toEndOf="@id/text1"
    app:layout_constraintTop_toTopOf="@id/text1"
    app:layout_constraintEnd_toEndOf="parent"
    android:background="@color/colorPrimary"/>
<TextView
    android:id="@+id/text3"
    android:layout_width="0dp"
    android:layout_height="0dp"
    app:layout_constraintStart_toEndOf="@id/text1"
    app:layout_constraintBottom_toBottomOf="@id/text1"
    app:layout_constraintEnd_toStartOf="@id/text4"
    app:layout_constraintTop_toBottomOf="@id/text2"
    android:background="@color/colorAccent"
    app:layout_constraintHorizontal_weight="1"/>
<TextView
    android:id="@+id/text4"
    android:layout_width="0dp"
    android:layout_height="0dp"
    android:background="@color/black"
    app:layout_constraintStart_toEndOf="@id/text3"
    app:layout_constraintTop_toBottomOf="@id/text2"
    app:layout_constraintBottom_toBottomOf="parent"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintHorizontal_weight="2"/>

类似于LinearLayout的属性

app:layout_constraintHorizontal_weight

该属性与LinearLayout的layout_weight使用类似

layout_constraintHorizontal_chainStyle

app:layout_constraintHorizontal_chainStyle="spread"

spread，默认属性，当宽度为0时按照weight分配宽度，宽度非零时：

spread-inside，宽度非零时：

packed，宽度非零时：

增加浮动效果

app:layout_constraintHorizontal_bias="1"
app:layout_constraintVertical_bias="1"

辅助布局

可通过定义辅助布局，对控件以辅助线为基准进行位置改变

<android.support.constraint.Guideline
    android:id="@+id/guide_h"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:orientation="horizontal"
    app:layout_constraintGuide_percent="0.5" />
<android.support.constraint.Guideline
    android:id="@+id/guide_v"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:orientation="vertical"
    app:layout_constraintGuide_percent="0.5" />
<TextView
    android:layout_width="50dp"
    android:layout_height="50dp"
    android:background="@color/red"
    app:layout_constraintStart_toEndOf="@id/guide_v"
    app:layout_constraintTop_toBottomOf="@id/guide_h" />